C / C++ / MFC

20-Nov-05 18:33

Hi all

,
Please help me out with this one.
I have made a Dialog-based app (MyDialog). I added a class of my own(MyClass) to this application.
MyDialog uses MyClass. So i did a #include "MyClass.h" in MyDialog.cpp
Later on i realised that MyClass requires MyDialog class. So i did a #include "MyDialog.h" in MyClass.cpp.
Now when i compile, i get an "Undelcared Identifier" error at:
enum {IDD = IDC_MY_DIALOG};
Sigh | :sigh:

I tried changing the locations of the #include to all possible places (including StdAfx.h).
Please help me out everyone. Am i missing anything???? How should i include the headers when two files are interdependent. Confused | :confused:

Thanks in advance!

*** Who said nothing is impossible? I have been doing it since a long time ***

kakan20-Nov-05 20:40

20-Nov-05 20:40

Hello.

You can use the concept of "forward declaration". That is: You just declare the class in one of the header files, for instance, in MyDialog.h:

class MyClass;

class MyDialog ... {
....
};

Kakan

Cool^ASL20-Nov-05 21:50

20-Nov-05 21:50

Hi Kakan,
Thanks for the quick reply.
I think i have tried a forward declaration earlier.
But let me double check if i had done it correctly.
So, should i make forward declaration in both the files for the other class.
Like:

MyDialog.h

class MyClass<br />
class MyDialog<br />
{<br />
....<br />
};

and then

MyClass.h

class MyDialog;<br />
class MyClass<br />
{<br />
....<br />
};

Should i continue to include the header files in each of the file as i have been doing?

In MyClass, i dont require to make MyDialog object a member. i am just using it in one of the functions of MyClass.

Please reply.

*** Who said nothing is impossible? I have been doing it for a long time ***

kakan20-Nov-05 23:59

20-Nov-05 23:59

Hello, and I'm sorry for the delay. I'm at work, you know and I have to make a living too... Smile | :)

This situation really isn't very easy to get going, but it is possible.

Try this:
In MyDialog.h:

class MyClass;
class MyDialog
{
....
};

In MyDialog.cpp:
#include "MyDialog.h"
#include "MyClass.h"

And make sure that each of the h-files can be included just once.

I.e:

#ifndef MY_DIALOG_H
#define MY_DIALOG_H

... definition of MyDialog

#endif

Cool^ASL21-Nov-05 0:03

21-Nov-05 0:03

Well Kakan,
i dont have the code with me right now.
I'll try it out and tell you tomorrow.
Thanks a lot for the help.
I'll contact you tomorrow.

Thanks a lot.

*** Who said nothing is impossible? I have been doing it for a long time ***

kakan21-Nov-05 0:20

21-Nov-05 0:20

OK. I'm using the trial and error-method when I have to get a construct like this to compile.
It gets a lot of errors... Sigh | :sigh:

Good luck.
Kakan

Cool^ASL21-Nov-05 18:16

21-Nov-05 18:16

Hi Kakan,
It was just a silly fault on my part.
i am extremely sorry about the whole matter.
During the initial phase, i had commented out the resource.h file.
Moreover, i had declared one function in MyClass.h but forgot to define it in MyClass.cpp. That gave a linker error and showed the mangled names of the function. Since the names were not so clear, i skipped reading it everytime.
Yesternight, i looked more closely to the error and read each line of it then realised my mistake.
No forward declaration was required. I created another simple C++ project and simulated the same situation, but it worked out.

Thanks for all the help.
And, sorry that i bothered you.

Thanks a lot!

*** Who said nothing is impossible? I have been doing it for a long time ***

kakan21-Nov-05 19:15

21-Nov-05 19:15

;);)
As the Aussies would put it: No worries mate!

Problem solved, that's the main thing.
And you've learnt your lesson. IMO, it's the knowledge that comes the hard way, that's stick to ones mind.

Keep on going!

Cool Ju20-Nov-05 22:43

Cool Ju

20-Nov-05 22:43

Hi,

try including resource.h in myclass.cpp. Hope it works.

Bye
Cool Ju Cool | :cool:

Dream Ur Destiny

Cool^ASL20-Nov-05 23:21

20-Nov-05 23:21

Hi Cool Ju,
thanks for your help.
I tried that too. But the problem is not solved by that.
I think Kakan is right. It must be something related to forward declaration.
Please tell me if you have any idea regarding that.

Thanks a lot.

*** Who said nothing is impossible? I have been doing it for a long time ***

Cool Ju20-Nov-05 23:33

Cool Ju

20-Nov-05 23:33

Hi,

Where did u added. Add in CMyclass.cpp ie where u added the CMyDialog.h

Its working for me.

Bye,
Cool Ju Cool | :cool:

Dream Ur Destiny

Cool^ASL20-Nov-05 23:41

20-Nov-05 23:41

Well, i dont have the code with me right now...
I'll try it and tell you tomorrow.

Thanks a lot, man. Thanks for the help.

*** Who said nothing is impossible? I have been doing it for a long time ***

Cool^ASL21-Nov-05 18:19

21-Nov-05 18:19

Hi Cool Ju,
It was just a silly fault on my part.
i am extremely sorry about the whole matter.
During the initial phase, i had commented out the resource.h file.
Moreover, i had declared one function in MyClass.h but forgot to define it in MyClass.cpp. That gave a linker error and showed the mangled names of the function. Since the names were not so clear, i skipped reading it everytime.
Yesternight, i looked more closely to the error and read each line of it then realised my mistake.

Thanks for all the help.
And, sorry that i bothered you.

Thanks a lot!

*** Who said nothing is impossible? I have been doing it for a long time ***

karle21-Nov-05 9:31

karle

21-Nov-05 9:31

I think IDC_MY_DIALOG ist not defined.

Did you include resource.h in your Source ?
Is there a Dialog with this ID in your resource ?

Cool^ASL21-Nov-05 18:23

DLL Problem, Linker error. Need Help??

21-Nov-05 18:23

HI Karle,
Thanks for the help.
I had commented out "resource.h" in "stdafx.h"
Moreover, i forgot to define a function which i had declared in the header file. The linker error was so confusing that i wasn't able to understand the actual problem.

Now its working...
Thanks for the help.

*** Who said nothing is impossible? I have been doing it for a long time ***

Owner drawn20-Nov-05 17:58

20-Nov-05 17:58

Hi guys,

When I try to link a DLL I get this error message.

Cannot Find TestDLL even with argument lookup.

TestDLL is a function defined in the dll.

I am a newbie to DLL. I have done it in other languages but not in VC. Can somebody tell me how to go about this.

Also kindly tell me the basic steps for working with a DLL. Sniff | :^)

<marquee direction="up" height="30" scrolldelay="1" step="1" scrollamount="1" hspace="0" vspace="0">
--Owner Drawn
--Nothing special
--Defeat is temporary but surrender is permanent
--Never say quits
--Jesus is Lord

Cool Ju20-Nov-05 20:09

Cool Ju

20-Nov-05 20:09

Hi,

How r u linking the dll (explicitly - lib or implicitly - run time loading)

Check this[^] for tutorials

Bye
Cool Ju Cool | :cool:

Dream Ur Destiny

Owner drawn20-Nov-05 20:41

20-Nov-05 20:41

Runtime linking

ThatsAlok20-Nov-05 21:37

ThatsAlok

20-Nov-05 21:37

For Runtime Linking are you calling LoadLibrary(..) and GetProcAddress api?

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV

ThatsAlok20-Nov-05 21:35

ThatsAlok

20-Nov-05 21:35

Could you tell me your Flow... are you using LoadLibrary and GetProcAddress Api to dynamically load dll?

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV

Owner drawn20-Nov-05 22:34

20-Nov-05 22:34

I am using neither of them.

I just included the necessary files and then the library path in project settings.

I don't if I am right.

Will need help.

ThatsAlok20-Nov-05 23:44

ThatsAlok

20-Nov-05 23:44

Here A Small code that will demonstrate dynamically loading of function from DLL.here, I will load mciSendString defined in WINMM.DLL .

// first make Function pointer
typedef MCIERROR (WINAPI * MCISENDSTRING)(
LPCTSTR lpszCommand,
LPTSTR lpszReturnString,
UINT cchReturn,
HANDLE hwndCallback
);

/// In function where you want to use about api
MCISENDSTRING fnmciSendString=NULL;
HMODULE hLibrary;

// load the library
hLibrary=LoadLibrary(_T("winmm.dll"));

// check is library loaded
if(hLibrary)
{
// if yes try to get Function addressfnmciSendString=(MCISENDSTRING)::GetProcAddress(_T("mciSendString"));
}

// check is we got Function Pointer
if(fnmciSendString)
{
// if yes call function
(fnmciSendString)(......);
}

"Opinions are neither right nor wrong. I cannot change your opinion. I can, however, change what influences your opinion." - David Crow

cheers,
Alok Gupta
VC Forum Q&A :- I/ IV

Owner drawn21-Nov-05 0:45